1. Field of the Invention
This invention in general relates to the field of iontophoretic introduction of ionic substances into a body, and more particularly concerns an iontophoretic device in which the polarity of the electrodes is reversible, thus providing an iontophoretic instrument with a doubled capacity and improved performance capabilities.
2. Description of the Prior Art
Iontophoresis is a method for introducing ionic substances into a body. The method utilizes direct electrical current to drive the ionized substances, such as chemicals or drugs, through the intact skin or other body surface. This has proven to be useful in numerous medical applications. U.S. Pat. No. 3,991,755 issued to Jack A. Vernon, et al and U.S. Pat. No. 4,141,359 issued to Stephen C. Jacobsen, et al. disclose examples of iontophoretic devices and some applications of the devices. The iontophoresis process has been found to be useful in the administration of lidocaine hydrochloride, hydrocortisone, acetic acid, flouride, penicillin, dexamethasone sodium phosphate and many other drugs. Perhaps the widest use of iontophoresis is that of diagnosing cystic fibrosis by using pilocarpine nitrate iontophoresis. The pilocarpine nitrate stimulates sweat production; the sweat is collected and analyzed for its chloride content to detect the presence of the disease.
In iontophoretic devices two electrodes are used. One electrode, called the active electrode, is the electrode at which the ionic substance is driven into the body. The other electrode, called the indifferent or ground electrode, serves to close the electrical circuit through the body. For example, if the ionic substance to be driven into the body is positively charged, then the positive electrode will be the active electrode and the negative electrode will serve to complete the circuit. If the ionic substance is negatively charged, then the negative electrode will be the active electrode and the positive electrode will be the indifferent electrode.
In the prior art the polarity of the current source, and thus of the electrodes is fixed. Thus, for a given ionicity, one of the electrodes is always the active electrode, while the other electrode is always the inactive electrode. The active electrode includes a source of the ionic substance, while the indifferent electrode does not. In these prior art devices only one of the electrodes provides a source of the ionic substance. Further, if the electrodes are accidently connected to the wrong terminals of the current source the ionic substance will not be ionotophoresed. Further, in many such devices, if it is discovered that the electrodes have been reversed the device must be removed from the body, the electrodes replaced correctly and then the device must be reapplied.